1. Field of the Invention
The present invention is related to a level shifter and, in particular, to a high-performance level shifter for use with thin gate-oxide devices.
2. Discussion of Related Art
Circuit development is often a result of technological change. In the 1960's the N-channel MOS gate oxide thicknesses were about 2000 Å in order to support gate bias potentials of about 18 volts. In the last ten years, products that were designed with 130 Å thick gates for five volt supplies are now designed for operating supply voltages of 3.3 volts with core supplies of 2.5 volts. More recent designs with core voltages of 1.0 volts have 3.3 volt external drives with gate oxides of core transistors of 16 Å gate thicknesses. These later reductions to one volt supply designs now require the added expense of a dual oxide process, for example an 80 Å process for device potentials of 3.3 volts and a 16 Å process for device potentials of 1.0 volts. The lower device potentials can result in lower power consumption.
Further, many devices still utilize a higher voltage power supply, even when some of the integrated circuits are formed with thinner gate oxides (and therefore are designed for lower voltage applications). Application of voltages greater than the design specification for a particular gate oxide thickness can result in damage to the transistor. Further, application of high voltage power supplies in circuits that are formed with lower voltage transistors can affect the timing of those circuits.
Additionally, there is always interest in providing circuits that utilize less power, and therefore are less likely to damage the thin oxides, and that operate faster. Therefore, there is a need for circuits capable of switching between voltages at high speed while using low power so as to not damage the thin gate-oxides of the devices.